I keep trying new and different (or old and beloved) dirt pedals and keep going back to the Pigtronix Disnortion. It's got a decent smooth OD, a Muff-style Fuzz that has 6 EQ shapes to pick from - at least 3 or 4 of which work well with bass - and it's got an octave-drive section that can be used alone (it's kinda lo-fi and a decent synthy base for filtering or modulation) or stacked on top of the other two, which can themselves be used individually, or together in parallel. Really a lot of options in one box that can be had for about $100. Its fuzz is not the killer over-the-top mass of doom or snarl you'll get from a Supercollider, B:Assmaster, etc but I think less can be more, unless you absolutely need your fuzz to go to 11.